Real time volume confirmation of aspirated fluids, such as reagents, is very desirable during operation of a diagnostic instrument to confirm the accuracy of assay results. Erroneous results can occur when the fluid volume is less than the required amount and the low volume goes undetected.
For high throughput diagnostic instrument systems, conventional techniques to detect insufficient fluid volume, such as optical detectors, have inherent shortcomings. For these high throughput systems, there is typically not enough time to pull the whole fluid segment past the optical detector in such a fashion as to prevent the fluid stream from breaking into smaller segments. It is known that a liquid stream can break into smaller segments at high flow rates. This can result in small segments of the fluid not able to pass through the optical detector during the aspiration time period, and thus the volume will be erroneously flagged as too low. An additional drawback of using an optical detector is that the tail of the liquid stream is required to flow past the optical sensor, thereby reducing throughput of the system.
Real time fluid aspiration confirmation is needed to ensure that accurate fluid volume is used in assay analyses. This document describes a technique and algorithm for real time fluid aspiration confirmation.